Methods of making progressive lens surfaces are known in the art and are described, for example, in U.S. Pat. Nos. 4,676,610, 4,806,010 and 4,838,675. Finished progressive lenses are typically made from progressive lens blanks, i.e., optical bodies having a finished convex front progressive surface and an unfinished rear concave surface. The rear surface is normally finished to produce a lens which meets the wearer's prescription. The fitting of progressive lenses is more demanding than the fitting of conventional multifocals. In this regard, each progressive lens blank typically has two sets of markings, a temporary set and a permanent set, to assist in verification of power and in fitting the lenses to the patient's face. The temporary markings (or verification markings) usually consist of a fitting cross, which should fall within 2 to 3 mm from the center of the pupil, and a distance reference center mark and a near-reference center mark to use in checking the powers of the distance and near segment areas. Preferably, the temporary markings should be left on the lens until the position of the fitting cross can be verified on the patient's face.
The permanent markings are typically semi-visible, and consist of two mesas (or slight elevations) on the surface of a lens that establish the horizontal line at the optical center of the lens. Some manufacturers also place their own identification mark and the power of the add near the semi-visible marks on the temporal side of the lens.
In the event that the temporary markings are removed, they can be reconstructed by locating, marking, and placing the semi-visible marks over the manufacturer's centration chart, and then tracing the verification marks with a pen. If the lens is placed against a dark background and viewed with an intense light, the semi-visible marks can be seen more easily. Conventional methods of recreating the verification marks can be cumbersome and imprecise.